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Journal Articles

Intermittent $$beta$$ collapse after NBCD turn-off in JT-60U fully non-inductive reversed shear discharges

Takei, Nahoko; Nakamura, Yukiharu; Ushigome, Masahiro*; Suzuki, Takahiro; Aiba, Nobuyuki; Takechi, Manabu; Tobita, Kenji; Takase, Yuichi*; Fukuyama, Atsushi*; Jardin, S. C.*

Plasma Physics and Controlled Fusion, 49(3), p.335 - 345, 2007/03

 Times Cited Count:7 Percentile:27.89(Physics, Fluids & Plasmas)

Non-disruptive $$beta$$-collapses with a regular intermittency have been observed after a forced turn-off of neutral beam current drive (NBCD) in JT-60U fully non-inductive, reversed shear (RS) discharges. Self-consistent transport simulations with improved core confinement and linear MHD stability analysis have first clarified that redistribution of return current induced after the NBCD turn-off lowers the safety factor of magnetic shear reversal, leading to the n =1 kink-ballooning instability with localized modes around internal transport barrier (ITB). It was also pointed out that an increase of the bootstrap current under continuous NB heating can lead to ITB reconstruction and thus causes subsequent beta-collapses.

Journal Articles

A Simulation study on inductive ITB control in reversed shear tokamak discharges

Nakamura, Yukiharu; Tobita, Kenji; Fukuyama, Atsushi*; Takei, Nahoko; Takase, Yuichi*; Ozeki, Takahisa; Jardin, S. C.*

Nuclear Fusion, 46(8), p.S645 - S651, 2006/08

 Times Cited Count:3 Percentile:11.73(Physics, Fluids & Plasmas)

A self-consistent simulation, including a model for improved core energy confinement, demonstrates that externally applied, inductive current perturbations can be used to control both the location and strength of internal transport barriers (ITBs) in a fully non-inductive tokamak discharge. We find that ITB structures formed with broad non-inductive current sources such as LHCD are more readily controlled than those formed by localized sources such as ECCD. Through this external control of the magnetic shear profile, we can maintain the ITB strength which is otherwise prone to deteriorate when the bootstrap current increases.

Journal Articles

A Simulation study on stable current shutdown in non-inductive reversed shear tokamak discharges

Takei, Nahoko; Ushigome, Masahiro*; Suzuki, Takahiro; Nakamura, Yukiharu; Takase, Yuichi*

Europhysics Conference Abstracts (CD-ROM), 30I, 4 Pages, 2006/00

no abstracts in English

Journal Articles

Numerical simulation on current spike behaviour of JT-60U disruptive plasmas

Takei, Nahoko; Nakamura, Yukiharu; Tsutsui, Hiroaki*; Yoshino, Ryuji; Kawano, Yasunori; Ozeki, Takahisa; Tobita, Kenji; Iio, Shunji*; Shimada, Ryuichi*; Jardin, S. C.*

Plasma Physics and Controlled Fusion, 46(12), p.1815 - 1830, 2004/12

 Times Cited Count:1 Percentile:3.1(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

TSC simulation of ITB crash and following disruption dynamics on JT-60U high-$$beta$$ reversed shear plasmas

Takei, Nahoko; Nakamura, Yukiharu; Kawano, Yasunori; Tsutsui, Hiroaki*; Ozeki, Takahisa; Tobita, Kenji; Sugihara, Masayoshi; Iio, Shunji*; Shimada, Ryuichi*; Jardin, S. C.*

Europhysics Conference Abstracts, 28G, 4 Pages, 2004/00

no abstracts in English

Journal Articles

Axisymmetric MHD simulation of ITB crash and following disruption dynamics of tokamak plasmas with high bootstrap current

Takei, Nahoko; Nakamura, Yukiharu; Kawano, Yasunori; Tsutsui, Hiroaki*; Ozeki, Takahisa; Tobita, Kenji; Sugihara, Masayoshi; Iio, Shunji*; Shimada, Ryuichi*; Jardin, S. C.*

Journal of Plasma and Fusion Research SERIES, Vol.6, p.554 - 557, 2004/00

no abstracts in English

Journal Articles

Current profile behavior during ramping-up phase in high bootstrap current tokamak plasmas

Nakamura, Yukiharu; Tsutsui, Hiroaki*; Takei, Nahoko*; Shirai, Hiroshi; Sugihara, Masayoshi; Gribov, Y.*; Ozeki, Takahisa; Tobita, Kenji; Iio, Shunji*; Jardin, S. C.*

Journal of Plasma and Fusion Research SERIES, Vol.6, p.196 - 198, 2004/00

no abstracts in English

Journal Articles

TSC modelling of current ramp scenarios with ITB-Generated bootstrap currents in JT-60U reversed shear discharges

Nakamura, Yukiharu; Tsutsui, Hiroaki*; Takei, Nahoko*; Sakamoto, Yoshiteru; Fujita, Takaaki; Sugihara, Masayoshi; Ozeki, Takahisa; Tobita, Kenji; Konishi, Satoshi; Iio, Shunji*; et al.

Europhysics Conference Abstracts, 27A, 4 Pages, 2003/00

no abstracts in English

Journal Articles

Analysis of toroidal rotation effects of the ion polarization current on the neoclassical tearing mode

Takei, Nahoko; Ozeki, Takahisa; Smolyakov, A. I.*; Isayama, Akihiko; Hayashi, Nobuhiko; Iio, Shunji*; Shimada, Ryuichi*

Journal of Plasma and Fusion Research SERIES, Vol.5, p.386 - 389, 2002/00

no abstracts in English

Journal Articles

The Evaluation of mode purity for ECCD using single deep grooved polarizer

Saigusa, Mikio*; Kikuchi, Yusuke*; Takei, Nahoko*; Kanazawa, Sadayoshi*; Kasugai, Atsushi; Sakamoto, Keishi; Imai, Tsuyoshi

Fusion Engineering and Design, 53(1-4), p.505 - 510, 2001/01

 Times Cited Count:10 Percentile:57.68(Nuclear Science & Technology)

no abstracts in English

Journal Articles

New application of a deep grooved polarizer for ECCD

Saigusa, Mikio*; Takei, Nahoko*; Kanazawa, Sadayoshi*; Kikuchi, Yusuke*; Kasugai, Atsushi; Sakamoto, Keishi; Imai, Tsuyoshi

Journal of Plasma and Fusion Research SERIES, Vol.3, p.383 - 386, 2000/00

no abstracts in English

Oral presentation

Non-inductive operation scenario of plasma current ramp-down in CS-less, advanced tokamak reactor

Nakamura, Yukiharu; Tobita, Kenji; Takei, Nahoko; Takase, Yuichi*; Fukuyama, Atsushi*; Nishio, Satoshi; Sato, Masayasu; Jardin, S. C.*

no journal, , 

no abstracts in English

Oral presentation

Study of destruction and reconfiguration of internal transport barrier in non-inductive current plasma

Takei, Nahoko; Ushigome, Masahiro*; Suzuki, Takahiro; Takechi, Manabu; Aiba, Nobuyuki; Nakamura, Yukiharu; Takase, Yuichi*

no journal, , 

no abstracts in English

Oral presentation

External control of internal transport barriers using inductive current perturbation in noninductive tokamak plasmas

Nakamura, Yukiharu; Tobita, Kenji; Fukuyama, Atsushi*; Takei, Nahoko; Takase, Yuichi*; Ozeki, Takahisa; Jardin, S. C.*

no journal, , 

no abstracts in English

Oral presentation

A Simulation study on burning profile tailoring of steady state, high bootstrap current tokamaks

Nakamura, Yukiharu; Takei, Nahoko; Tobita, Kenji; Sakamoto, Yoshiteru; Fujita, Takaaki; Fukuyama, Atsushi*; Jardin, S. C.*

no journal, , 

From the aspect of fusion burn control in steady state DEMO plant, the significant challenges are to maintain its high power burning state of $$sim$$ 3 - 5 GW without burning instability, and also to keep its desired burning profile relevant with internal transport barrier (ITB) that generates high bootstrap current. A self-consistent simulation has pointed out that in the high power fusion DEMO plant there is a close, nonlinear interplay between the fusion burnup and the current source of non-inductive, ITB-generated bootstrap current. Consequently, as much distinct from usual burning conditions with lower power ($$<$$$$<$$ 1GW), the self-ignited fusion burn at a high power burning state of $$sim$$ 3 - 5 GW becomes so strongly self-organized that any of external means except fuelling can not provide the effective control of the stable fusion burn. The paper presents a simulation modeling of the burning stability coupled with the self-ignited fusion burn and the structure-formation of the ITB.

15 (Records 1-15 displayed on this page)
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